Budd units are strange looking, there's no doubt about it! But they use Lamb motors and while looking like a tin can and being LOUD work!
Filtration methods are up the the user. I prefer true cyclonic systems that vent outdoors, including any smell. Un-vented units of any kind can leave a bad smell in the air. I most hate cartridge filter systems, most notably the Electrolux/
Aerus foam cartridge filter! Getting all the dirt and the water out is hard. Not to mention the wet dirty mess you have on your hands. I'm also not a fan of MD open bag units. Getting the rubber gasket out as well as the bag and not getting any dirt in the bottom of the canister is hard,, and well, 12 gallons of dirt out of the canister takes a bit of muscle. I've serviced units where they are mounted too high on the wall and you need a step stool to get high enough to lift the bag out! But to each his own! We could take about the pro's and con's for days. But the trade is noticing more and more a shift toward bagged units. Just saying!
Ian! Sorry, you've been neglected as this thread has gone away from your needs to talk about filtration. Do not put a unit in the attic! As Tolivac said it can void your warranty. Unless, of course your attic is finished and climate controlled. Of course you'd also need to make sure you have an adequately sized outlet. As I said in another thread, sharing a circuit can be risky.
In a VDTA training class we learned about getting a branch line to a upper story and I've used the training several times. Scout around in your basement and see if you can find a closet on the ground (main) floor that also has a closet above it on your second story. If you do, you can run your branch line up from the basement through the closets and into your attic and then down to the # of inlets needed. I've even used this method in one of my homes to great success!
There are two more issues with your installation. First are those Budd inlets. You do not have to use them! The backup plate that the inlets attach to are universal. You are FREE to use any inlet made with a few exclusions! You are free to use either low voltage or dual voltage inlets with those mounting plates. Two, you are using the worst electric hose on the market! It's 1 1/4" wire wound and of all the hoses available is robbing you of the full power of your system! It's not crushproof and in the hose sock you are using you'd have a hard time seeing if someone trips on the hose or steps on it, crushing it some. If you upgraded your inlets AND your hose, you would utilize the FULL potential of your Budd system! It's an investment I'd make--you WILL see a difference. I am going to email you with my email and phone if yoju've more questions..
Greg Bushman